This Application Note discusses the sizing of neutral conductors in the presence of ‘triple-N’ harmonics– that is, currents with a harmonic order that is a multiple of three. This issue is particularly important in low voltage systems where harmonic pollution by single phase loads is an increasingly serious problem.
Triple-N harmonic currents add arithmetically with the result that neutral currents that are often significantly higher than the phase currents. Guidance on neutral sizing is given in IEC Standard 60364, Part 5-52: Selection and Erection of Electrical Equipment – Wiring Systems. This Application Note is intended to clarify the issues involved and present the IEC guidance to a wider audience.
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